use strict;
use warnings;

my $n = shift || 5;
my ($count, $first, $last) = (1, 0, $n - 1);
my @matrix;

push @matrix, [(0)] for (1..$n);
  {
  $matrix[$first][$_] = $count++ for ($first..$last);
  $matrix[$_][$last] = $count++ for (($first+1)..$last);
  $matrix[$last][$last-$_+$first-1] = $count++ for ($first..$last-1);
  for ($_ = --$last; $_ > $first; --$_)
    {$matrix[$_][$first] = $count++}
  $matrix[$first][$last] = $count if (++$first == $last);
  redo unless $first >= $last;
  }

my $width = (int log $count) - 1;
print "" . (join " ", map {sprintf "%${width}d", $_} @{$matrix[$_]}) . "\n" for (0..($n-1));